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WORLDS LARGEST GENV LT BY HPR




Completed HPR480 Short block


Here at Horsepower Research we are all about doing things in a big way. From our 468 LS engines all the way to our 5-2-7 tall deck LS, we like to do things bigger than the rest.

Recently Elie Bejjani at High Performance Connection in Houston contacted us on doing the largest Gen V LT engine. Elie having been a customer of ours for a number of years now, already has one of our 523 CID tall decks in his C6Z, as well as having a 472 LS, and a host of other engines we have build for him and his company. Taking on the challenge of the world largest LT seemed like the next logical step.

Starting foundation for this engine was a 5.3L Gen V Truck aluminum block. Unlike the prior Gen IV engines, the Gen V blocks all seem to share the same cross vented main design of the LS2/LS3/LS7 which is an added bonus for bay to bay breathing. Also to note is that the truck blocks have piston squirters as well like the Corvette and Camaro 6.2L blocks, which in this application we will not be using.


bare cylinder block


A specially modified K1 Technologies forged crankshaft is being used in this build that has been machined for the increase in stroke as well as fully Omicron finish polishing process once finished.


Polished forged K1 crank


Along with the crankshaft we also chose to have the connecting rods finished with the Omicron polish as well. These forged pieces are from Callies in their CompStar line with ARP 2000 series bolts.


connecting rod Omicron finish

Now some might be asking why polish the crankshaft and rods? Two reasons really, one was for the magazine shoot as it does improve the look of the parts and the other is the actual finish of the parts themselves. The Omicron® surfaces are slowly refined without the use of chemically accelerated etching such as a REM treatment. The process eliminates microscopic machining lines and imperfections, resulting in a surface topography that has both improved endurance and a reduced coefficient of friction. What this means inside the engine is that oil will shed from the parts and you would have a smoother finish for the journals as well. You have probably noticed we touched a bit on surface finishes with some of the new camshafts from Comp Cams recently as well. All about to drop frictional losses inside your engine, the concept is the same here too.

For pistons we again are working with Wiseco. Wiseco was one of the first to have a piston kit for the GenV engines and offers a number of "shelf stock" pistons in their pro series for the 5.3L and 6.2L engines with stock and increased stroke crankshafts. Of course this is no "shelf" piston but it did mean they had data on file for critical locations of the valve and injector pocket as well as actual testing from their own designs for weak points. Something you might notice with the piston is the color. Wiseco does a number of things for their DI engine pistons and that is include a heavy wall wrist pin as well as finish the pistons with their Armor Coating to help prevent damage due to detonation. Wiseco felt the stresses from the direction injection environment as well as increased compression ratio's needed to have the coating for increased reliability. You will find a number of their sport compact turbo pistons come with this finish as well.



HPR custom designed pistons by Wiseco

If you would like to learn more about the Armor Coating process you can read about it here: Wiseco Blog on Plating We do offer this, along with other coatings if the customer is interested on any of our builds.


Wiseco typically does the standard GenV kit's with an included 0.200 wall piston pin, We moved over to one of Wiseco's double taper pins for this build. This way we can retain the strength around the connecting rod but make the pin lighter near the ends were the added material is not as needed in this particular application. Again this is something we can do with just about any build. This reduces pin weight from 134 grams down to just 109 grams, but again gives us a nice thick wall pin in the connecting rod location.



double taper pins



Here you can see Wiseco's typical 0.200 wall pin that is included with shelf DI piston kits.




Once our block was sleeved with a set of Darton ductile iron sleeves we went about the process of finishing the cylinders off to size, decking the block flat, line honing mains to size and clearance any required areas for the increased stroke. Now it should be stated this was a first run build for this engine and checking for stroke clearance was done a number of times and the block was only cut where needed to minimize material removal from the cylinder liners or block.


Assembly is performed like all of our builds, care is taken along each step of the way to measure bearing clearances, crankshaft thrust movement, side clearances on connecting rods, wrist pin to piston clearances...to insure each engine is going to perform to the best of it's ability in service.


Checking main clearances


Setting up to measure thrust in the block



Checking ring gap

Once we had clearances done, bearings were installed in the block and rods. Rods and pistons were hung and secured with Wiseco's spiral locks, while the crankshaft was held in place by ARP hardware. Rings filed and cleaned prior to install to the pistons. Cylinders cleaned, and lightly oiled with the piston and rod combo being dropped in place.



First piston and rod to go in


One side finished up



The business end.



The short block was delivered to the customer over the weekend so at this time I do not have any status updates. Elie and the crew at HPC will be finishing out the long block with Greg Good ported heads and more. I will update when I get results in!

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Elie and the group at HPC in Houston finished up the project this week and started producing results last night on the dyno!!

Worlds largest LT, and I believe right now the worlds highest NA HP too!

chuntington101

Amazing results! What intake was the 700+ hp pull with? Any plans on fitting something a little better flowing as I guess that’s the limit at the moment? Also what fuel system fid this car use?

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Intake was the MSD as shown in the video.

You would have to talk to Elie Bejjani at HPC in Houston on the details of the car as they did the finish out, install and tune.

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The guys at HPC are working on tuning and will be doing some intake manifold testing later this month to see if they can get the 480 to make a little more still.

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Update on our HPR 480 cid LT engine as the guys at HPC have been working on their cylinder head design and testing a number of different intake manifolds.

First lets do a little recap. Their 2018 1LE Camaro (I know not a Vette but what they had to go testing with) had put down about 390-400 whp on their mainline dyno completely stock. After some bolt on parts (headers, MSD intake, cam change) they were making about 550 whp. Switching to the CID cylinder heads ported by Greg Good they moved up to right at 600 whp. Going to our 480 cid short block, cam change and bolting the same heads and intake manifold on they produced over 700 hp at the rear wheels.

Never enough, the guys moved to a Holley Hi-Ram intake manifold and larger TB to move into the low 700 range, I believe peaking just over 730 hp to the tires, so a good gain over the MSD intake but it did require modifications to the car and hood to fit the intake manifold.

Back under the knife, Greg changed his port design ever so slightly, a new larger top was made for the High Ram lower which was port matched, a 112mm TB installed as well as a 5.0" inlet pipe to feed it with a resulting 772 hp at the tires, peaking at almost 7000 RPM.

This is a normal hydraulic roller setup using Hy-Lift Johnson lifters, OE rockers with trunion upgrades. It is running on pump E85 fuel, and was doing so during all of the testing.


Trunion upgrade kit



480 baseline testing with MSD intake



Holley stock lid vs HPC/Greg Good modified Visner lid.



TB's tested ranged from stock, to ported, LT5 all the way to the 112 NW.



Blue: bolt ons, Red stock short block with CID heads, Yellow is CID heads on HPR 480 short block with MSD intake.





Greg Good CID LT heads in process



Greg Good CID intake port



New lid, 112tb, and massive air inlet



Dialing in the new lid and TB setup with the revised CID head port. Almost 400 more hp to the tire than what it was stock.


The guys did experiment with adding port injection to the car as well, but only saw minimal gains power wise, but did say it helped some of the low speed drivability.


Now that the weather is getting cooler out, plans are to get it to the track soon for times!

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More updates to the build and insight into the long block portion.

GenV LT makes 778 rwhp